Heat exchanger



July 18, 1967 PAULS 3,331,436

HEAT EXCHANGER Original Filed June 12, 1963 3 Sheets-Sheet 1 IIIIA'I'II" 2M A 5&4

A T TOR/V63 1N VENTOR.

i THERO/V FPAULS July 18, 1967 F. PAULS 3,331,436

HEAT EXCHANGER Original Filed June 12, 1963 3 sheetsshee INVENTOR. THERON F FA ULS A T TORNEY July 18, 1967 P U S 3,331,436

HEAT EXCHANGER Original Filed June 12, 1965 3 s-Sheet 5 INVENTOR. THERO/V F PAULS A TTORNE Y United States Patent 3,331,436 HEAT EXCHANGER Theron-F. Pauls, Godfrey, 11]., assignor to Olin Mathieson Chemical Corporation, a corporation of Virginia Continuation of application Ser. No. 375,409, May 18, 1964, which is a division of application Ser. No. 287,240, June 12, 1963, now Patent No. 3,273,227, dated Sept. 20, 1966. This application Jan. 25, 1966, Ser- No. 532,034

6 Claims. (Cl. 165170) This application is a continuation of application Ser. No. 375,409, filed May 18, 1964, now abandoned, which is a division of application Ser. No 287,240, filed June 12, 1963, now Patent No. 3,273,227 granted Sept. 20, 1966-.

This invention relates generally to heat exchange devices and more particularly to single piece sheet metal heat exchange structures having secondary heat dissipating fins integrated therewith.

A commonly used and efiicient type of heat exchange unit for evaporators, air conditioning, condensers, internal combustion engine cooling radiators and the like is formed from a plurality of superimposed sheets of metal and having internally disposed between the sheets a number of conduits generally in a parallel spaced arrangement extending from a first or intake header to a second or outlet header. One or more of such units may be employed; and the conduits or tubes serve to carry a heat exchange medium such as water or other coolant in conductive relationship with another medium such as air or other gas passing between the tubes. This type of construction is typical of automobile radiators where, for example, the heated water issues from the cooling block of the engine with the aid of a pump, first enters one of the two headers, and then passes through a great number of thin-walled, relatively flat, closely spaced tubes between which cooling air is blown and which extend usually vertically from one to the other of the headers. Condensers are also frequently of this same type of construction.

According to one known method of manufacture as illustrated in US. Patent 2,690,002, this type of heat exchange unit may be readily manufactured to provide a great multiplicity of tubes in a sheet of metal. This method involves the application of a suitable predetermined pattern of weld inhibiting material between component sheets, pressure welding all adjoining areas except those separated by the weld inhibiting material, thereby forming a unified composite panel, and inflating along the unwelded areas to erect the tubes integral with the resultant tubed panel. Full advantage heretofore has not been taken of this method inasmuch as the tubes formed are of rather fiat or oval shape with the major dimensions lying within or parallel to the panel in which the tubes are formed. In many applications it is desirable that the tubes extend not only longitudinally but also extend perpendicularly out of the panel to a considerable extent so as to place a greater number of the tubes in spaced parallel relationship rather than a lesser number in the same plane. This design adapts the units to fabrication as single pieces of large size, a lesser number of which may then be put together for installations where the external medium passes through perforations in the panel transversely to it rather than passing parallel to the panel along its surfaces,

In accordance with one aspect of this invention a sheet metal panel is formed according to the procedure of the above mentioned US. Patent No. 2,690,002, to form the desired tubular passageway system in its embryonic form. This panel is then slit along a plurality of parallel spaced apart lines extending between two oppositely disposed headers to define the interconnecting tubes. The tube ice portions lying between adjacent slits are then bent or twisted out of the normal plane of the panel so as to dispose the tube portions in substantially perpendicular relationship to the plane of the panel.

In order to improve the heat transfer characteristics of the device, secondary heat dissipating fin material is inserted between the parallel opposing surfaces or rolls of adjacent tubes and secured in place as by brazing or soldering. This construction, while extremely simple to fabricate and assemble, presents a practical and highly efiicient heat exchanger adapted to provide a maximum amount of external heat exchange medium flow between the tubes with a minimum amount of turbulence or impediment thereto.

Having thus generally described my invention it becomes a principal object thereof to provide a compact and highly efiicient heat exchange device adapted for transfer of heat between an internal and external heat exchange medium.

Another object of the present invention is to provide a heat exchange device having a plurality of parallel heat transfer tubes interconnected between a pair of headers for maximum flow of an internal heat transfer medium.

Still another object of the present invention is to provide a heat transfer device having a plurality of heat transfer tubes interconnected between a pair of headers, the tubes being elongate in cross section with the cross sectional major dimension of the tube being disposed at substantially right angles to the normal plane of the panel from which the device is fabricated.

Still another object of the present invention is to provide a heat exchange device having a plurality of heat transfer tubes interconnected between a pair of oppositely disposed headers which are bent or twisted out of the normal plane of the panel from which the device is fabricated so as to provide slots or apertures through which an external heat transfer medium may flow unimpeded over the external surfaces of the heat transfer tubes.

It is still a further object of the preesent invention to provide a heat exchange device having a plurality of heat transfer tubes interconnected between a pair of headers and having the major cross sectional dimension disposed at substantially right angles to the normal plane of the panel from which the device is fabricated to provide elongate apertures in which secondary heat dissipating fin stock material is inserted in heat transfer relationship with the outer walls of the tubes to achieve maximum efliciency of heat exchange between the internal and external heat transfer mediums.

Yet another object of the present invention is to provide a heat exchange device for use as automobile radiators, cooling system condensers and evaporators and the like, which is highly efiicient, compact, and economical to manufacture.

Further objects and advantages of the present invention will become apparent from the following :detailed description when considered in conjunction with the accompanying drawings, in which:

FIGURE 1 is a plan view of one embodiment of the completed heat exchange device of this invention;

FIGURE 2 is a composite plan view illustrating a number of steps involved in the fabrication of the device of FIGURE 1;

FIGURE 3 is a sectional view taken on line 33 of FIGURE 2;

FIGURE 4 is a view similar to FIGURE 3 illustrating the device in an intermediate stage of fabrication;

FIGURE 5 is a fragmentary View similar to FIGURE 4, but on an enlarged scale, illustrating a further stage in the fabrication of the device;

FIGURE 6 is a fragmentary sectional view on an enlarged scale taken on line 6-6 of FIGURE 1;

FIGURE 6A is a view similar to FIGURE 6 illustrating differential wall thickness between the headers and the tubes;

FIGURE 7 is a fragmentary section view on an enlarged scale taken on line 7-7 of FIGURE 1; and

FIGURE 8 is a fragmentary view illustrating an alternate embodiment of the invention.

Referring now to the drawings and particularly to FIGURE 1, there is seen an illustrative embodiment of this invention which is a heat exchange device generally indicated by the reference numeral 10. The initial stage of fabrication of this device is substantially as set forth in great detail in the above mentioned US. Patent 2,690,- 002, and is generally illustrated, in conjunction with other steps in the formation of the heat exchange device 10, in FIGURES 2, 3 and 4.

Referring now to FIGURE 2 it will be seen that the heat exchange device 10 is initially formed from a plurality of superposed flat metal sheets 12 and 14. Sheet 12 has applied thereto a pattern of weld preventing material 16 which is a foreshortened version of the desired pattern of tubular passageways in the finished article. This pattern consists of a pair of parallel bands 18 and 20 which are spaced apart adjacent a pair of opposite edges of the stack of sheets formed by the individual sheets 12 and 14. Interconnecting the two bands 18 and 20 are a plurality of bands 22 of weld preventing material which cover the extent of sheet 12 intermediate bands 18 and 20 except for elongated parallel islands 24 which are free of weld preventing material, and which also extend between the aforementioned bands 18 and 20. It will become apparent that the bands 18 and 20 of weld preventing material correspond to the headers in the finished article and that the bands 22 correspond to the plurality of interconnecting tubes. In order to provide ingress and egress apertures for heat transfer medium, the bands 18 and 20 are extended to an edge of sheet 12 as indicated at 26. It will also be seen that a marginal portion of sheet 12 :along opposite sides transverse to the aforementioned opposite sides has been left free of weld preventing material 16 is surrounded by a peripheral marginal area 28 with the exception of the two strips 26 extending to one of the transverse edges for the ultimate provision of openings adapted for connection to an external source of heat transfer medium.

1 The stack of component sheets 12 and 14 with weld preventing material 16 sandwiched therebetween is then temporarily secured together as by clamps, spotwelding or the like to prevent relative movement between the sheets 12 and 14. The assembly thus formed is then heated to a required temperature and fed through a pair of pressure rolls which exert sufiicient pressure on the stack to firmly weld the sheets 12 and 14 together into a single integrated sheet in the areas not coated with the weld preventing material 16. Simultaneously with the bonding operation the sheets 12 and 14 undergo a substantial reduction in thickness as well as an elongation in the direction of rolling whereby the foreshortened pattern of weld preventing material is stretched to a length corresponding to the desired pattern of tubular passageways in the finished article. FIGURE 4 illustrates in cross section the unified sheet30 with the unwelded portions 32 at this stage of the fabrication.

Referring again to FIGURE 2 it will be seen that a plurality of slits 34 are formed in the islands 24 free of weld preventing material, the slits extending almost the full length of these islands. An additional slit 36 is provided in the transverse marginal area free of weld preventing material for a purpose hereinafter to become apparent. The slits 34 and 36 may be formed during any desirable stage of the fabrication process, either in the individual sheets 12 and 14, or after the sandwich of sheets 12 and 14 and weld preventing material 16 has been formed and temporarily secured together or still alternatively after the aforementioned hot rolling step.

Preferably the last mentioned alternative would be selected so as to eliminate both the problem of proper alignment of individual sheets 12 and 14 with slits already formed therein, and the problem of rewelding of adjacent slit edges during the hot rolling step if no weld preventing material is inserted between these edges. However, it is apparent that the article is readily adaptable to any of a number of arrangements of the aforementioned steps to achieve the heat exchange device in its embryonic form as illustrated in cross section in FIGURE 4.

A still further alternative to the formation of the slits is form the panel in embryonic form as seen in FIGURE 4 but without the slits, subject it to the foregoing hot rolling, and then as more fully explained hereinbelow, inflate the unjoined portions of the panel defined by the areas of weld preventing material. Subsequent to this, the inflated panel is subjected to a combination shearing and turning tool which simultaneously parts the metal to form the slits and rotates the inflated tubes.

Subsequent to the pressure Welding stage in the fabrication process, the unwelded areas-26 which extend to the traverse edge of the unified sheet 30 are mechanically pried open and a suitable nozzle is inserted therein and connected to an external source of pressure fluid. The pressure fluid is pumped into the unwelded portions defined by the weld preventing material 16 to expand the sheets 12 and 14 over these portions and thereby create the desired system of internal fluid passageways. The expansion may be carried out either without external restraint thereby resulting in passageway walls having a rounded configuration, or preferably the expansion may be carried out with the composite sheet 30 inserted between suitable dies or plattens, either flat or shaped, so as to limit the extent to which the passageway walls can expand outwardly, thus creating a tubular passageway of generally rectangular configuration in cross section as seen in FIGURE 5.. The heat exchange device now consists essentially of the flat unified sheet 30 with an expanded pattern of tubular passageways corresponding to the original pattern of weld preventing material 16, with the bands 18 and 20 forming the headers 40 and 42.

Referring again to FIGURE 1, the heat exchange device 10 comprises the integrated sheet 30 of generally rectangular configuration, having the parallel spaced apart internally disposed headers 40 and 42 and the elongate tubular passageways 38. The headers 40 and 42 terminate adjacent an edge of sheet 30 in inlet and outlet openings 44 and 46 respectively to which conduits 48 and 50 respectively are connected for communication of the heat exchange device with a source of internal heat transfer medium.

It will be seen from FIGURE 1 and in greater detail in FIGURE 6 that the tubular passageways 38 have been twisted out of the normal plane of sheet 30 so as to dispose the major cross sectional dimension of tubes 38 at approximately right angles to the normal plane of sheet 30. This disposition of tubes 38 is accomplished by. any

desirable means, and has an extent covering substantially all of the length of the slits 34 previously formed in the unified sheet 30. As indicated above, the slitting mayoccur simultaneously with the tube rotation by the use of a combination tool. Thus in the finished product the individual tubes 38 are disposed with opposed parallel outer wall surfaces 52in spaced apart relationship, providing relatively wide and elongate slots or apertures 54 through which an external heat transfer medium can flow substantially unimpeded. Communication between the headers 40' and 42 and interconnecting tubes 38 is maintained through the interior of the tubes 38 Which traverses the transition portions 56 of tubes 38 which lie between the point of connection between the headers 40 and 42 and the remainder of the tubes 38 which are disposed in the aforementioned perpendicular relationship. 0f course,it' is desirable to maintain these transition portions 56 as.

short as possible within the limits of the bending characteristic of the metal in order to provide the maximum length of apertures 54for unimpeded flow of air and, as will be seen in more detail hereinbelow, to provide the maximum amount of space for secondary heat dissipating fins. I

During rotation of the tubes, these transition portions 56 may be allowed to collapse and be reinflated in the weakened state during a subsequent brazing operation, more fully explained below. In the alternative, it may in some instances be desirable to insert in the headers 40 and 42 a tool similar to a comb and insert the pins or teeth thereof into the tubes 38 and rotate them around these pins or teeth, thereby preventing collapse.

It should be noted that, as with the aforementioned slitting step to provide the slits 34 and 36, it is alternative whether the twisting step to dispose the tubes 38 out of the normal plane of the unified panel 30 is carried out before orsubsequent to the inflation step, or simultaneously therewith. One advantage to performing the twisting step after inflating the embryonic panel 30 lies in obviating the inherent difliculties involved in placing the panel 30 between the aforementioned dies or plattens with tubes 38 already bent at right angles to the plane of the remainder of panel 30. Also slitting and rotating subsequent to inflating eliminates the problem of identifying the location on the panel of the islands 24 in which the slits are to be made.

Whateverv the sequence of the aforementioned events, when the tubular passageways have been completed and the interconnecting tubes 38 bent to the'desired relationship secondary heat dissipating fins 58 formed of closely corrugated or pleated fin stock may be inserted and positioned within the elongate spaces or apertures between the opposing faces 52 and tubes 38, and suitably secured therein by conventional means, such as solder, brazing and the like interposed between the panel and the fin stock. It is also possible to insert the fins before the tubes are fully inflated so that they will easily drop into place, after which additional pressure is applied during the brazing operation to insure intimate contact of the fins with the tubes. In one form this fin stock may be formed by bending strips of highly heat conductive metal into a corrugated or serpentine form. Itwill be noted from FIG- URE 6 that when the tubes 38 are bent, the welded portions of sheets 12 and 14 formerly defined by the islands 24 free of weld preventing material now constitute oppositely directed flangers 60, thereby leaving the opposing faces 52 of tubes 38 smooth and free of any projecting obstructions. Consequently, it is a relatively simple matter to slip the strips of fin stock 58 into place between adjacent tubes for subsequent unification therewith as explained above. In addition the flanges 60 add structural rigidity to the device and also reinforce the leading edge of the tubes for minimizing damage thereto due to stones or other foreign objects which can strike the frontal area of an automotive radiator. Also the flanges constitute additional heat transfer stock.

In order to secure the outermost rows of fin stock 62 and 64 in place, outer retaining strips 66 and 68 are formed by providing the two outermost slits 36 (FIG- URE 1) beyond the pattern of weld preventing material 16. Thus, during the hot rolling process a strip of sheets 12 and 14 is bonded together between the outermost slits 36 and adjacent slits 34 which, when twisted in the same manner as tubes 38, form the outer retaining strips 66 and 68 respectively.

In the manufacture of automobile radiators and the like, a plurality of the resultant blanks 30 may be assembled in face to face relationship with the tubes and the elongate spaces or apertures in alignment with the corresponding tubes and apertures in adjacent panels, or the tubes of one panel may be in overlapping relationship with tubes of adjacent panels, wherein secondary fin stock is individually inserted in each panel prior to assembly. In a still alternate procedure, the plurality of panels may be assembled in face to face relationship prior to secondary fin stock insertion wherein the tubes and the apertures of one panel are in alignment with the corresponding tubes of the adjacent panels. Thereafter, appropriate secondary fin stock may be inserted in the apertures between tubes, so that the fin stock will be coextensive with the assembled plurality of panels, that is the fin stock extends through all of the panels.

Several embodiments of the foregoing structure and alternate methods of fabrication are apparent. One such modification is illustrated in FIGURE 8 and has for its purpose a closer spacing between the tubes interconnecting the spaced apart headers, thereby minimizing the amount of space required for a given unit with a predetermined amount of heat exchange ability, either with or without secondary fin stock material. To achieve this configuration the device is initially fabricated with the tubes spaced, for example, on approximately 1 /2" centers; the tubes are then rotated as in the foregoing embodiment, after which the headers are collapsed between the tubes such as is done in bellows-type flexible metal tubing, etc. This produces corrugations or undulations in the headers having the ridges and valleys 70 and 72 respectively such as in FIGURE 8. The tubes, which originally were on the 1 /2" centers, would be brought down to approximately /s" to /2" centers, or other predetermined spacing, after which the secondary fin stock could be inserted between the tubes, if desired, as described above. This also would tend to strengthen the headers which would be of the same wall thickness as the tubes.

It may in some instances be desirable to produce a heat exchange device in accordance with the principles of this invention in which there is a differential in wall thick ness between the headers and the tubes. This may be accomplished, for example, by the use, during the initial rolling process to form the unexpanded panel, of a stepped roll which would roll the tube thickness from say .030" down to .010" prior to rotating the tubes. This results in a reduced gauge tube while keeping a heavy wall in the headers.

Such a relationship is illustrated in FIGURE 6A, analogous to FIGURE 6 previously described. Following the procedure just described, the panel 30 of FIGURE 4 in the area of the tubes would be decreased in thickness relative to the header section resulting in the modified panel shown in FIGURE 6A. For example, note the thinner tube wall thickness at 152 in FIGURE 6A relative to the header wall thickness illustrated at in FIG- URE 6A.

It should be noted, however, that this procedure would elongate the area of the panel between the headers three times that of the corresponding panel rolled without the use of a stepped roll, thereby resulting in tubes in the finished article having a length three times that otherwise obtained. After rolling, the tubes would be slit, rotated, inflated and secondary fin stock inserted therebetween or not as desired.

It should be noted that with any of the above embodiments and alternate methods of fabrication, as much cooling capacity as required may be achieved by arranging the heat exchange units in multiples with the headers of the several units being connected in parallel.

It will be apparent from the foregoing description and accompanying drawings that there has been provided a heat exchange device which is believed to provide a solution to the foregoing problems and achieve the aforementioned objects. It is to be understood that the invention is not limited to the illustrations described and shown herein which are deemed to be merely illustrative of the best modes of carrying out the invention, and which are susceptible of modification of form, size, arrangement of parts, and detail of operation, but rather is intended to encompass all such modifications as are within the spirit and scope of the invention as set forth in the appended claims.

What I claim and desire to secure by Letters Patent is:

1. A heat exchange device having improved heat transfer characteristics comprising:

(A) a substantially flat, planar composite sheet metal unit having a pair of parallel oppositely disposed spaced apart marginal portions,

(1) said marginal portions having internal tubular passageways disposed between spaced apart portions of the thickness of said sheet,

(2) said passageways extending to an edge of said sheet to provide ingress and egress openings for a fluid,

(B) a plurality of individual strips of said unit each interconnecting said marginal portions,

(1) said strips each being of a thickness substantially less than the thickness of said marginal portions and having an elongate portion which is substantially rectangular in cross section with its major dimension along substantially the full length thereof disposed in a plane substantially perpendicular to the plane of said unit, said elongate portion being integrated at each end thereof with a transition bend portion through which said strips are integrated with said marginal portions of said unit whereby said strips over said elongate portion are disposed in parallel spaced apart relationship with their outer planar surfaces in face to face relationship, thereby defining elongate apertures for the flow therethrough of an external heat tarnsfer medium,

(2) said strips having an internal tubular passageway disposed between spaced apart portions of the thickness of said strips, said latter passageways communicating with said passageways in said marginal portions thereby providing a continuous path for the circulation of a heat transfer medium through said unit.

2. A device as set forth in claim 1 wherein said strips terminate along their outer longitudinal edges in an outwardly projecting flange having a thickness corresponding to that of the unified portions of said composite sheet.

3. A device as set forth in claim 1 in which said marginal portions of said composite sheet are partially collapsed along the longitudinal axis of said marginal portions to form alternate ridges and valleys therein.

4. A device as set forth in claim 1 further including heat dissipating fins secured Within said elongate apertures.

5. A device as set forth in claim 1 further including at least one retaining strip parallel to, but spaced from, said plurality of individual strips,

(A) said retaining strip having an elongate portion which is substantially rectangular in cross section with its major dimension along substantially the full length thereof disposed in a plane substantially perpendicular to the plane of said unit, thereby defining an additional elongate aperture between said retaining strip and one of said individual strips,

(B) said retaining strip being devoid of internal passageways.

6. A device as set forth in claim 5 further including heat dissipating fins secured within said additional elongate aperture. 25

References Cited UNITED STATES PATENTS 7/1964 Adams 29-157.3 X 8/1956 Grenell et al. 29157.3 7/1959 Wurtz 29-1573 5/1961 Adams 29-157.3 8/1961 Reynolds 29 157.3 7/1965 Frornson 29-1573 X FOREIGN PATENTS 4/1960 France. 

1. A HEAT EXCHANGE DEVICE HAVING IMPROVED HEAT TRANSFER CHARACTERISTICS COMPRISING: (A) A SUBSTANTIALLY FLAT, PLANAR COMPRISING SHEET METAL UNIT HAVING A PAIR OF PARALLEL OPPOSITELY DISPOSED SPACED APART MARGINAL PORTIONS, (1) SAID MARGINAL PORTIONS HAVING INTERNAL TUBULAR PASSAGEWAYS DISPOSED BETWEEN SPACED APART PORTIONS OF THE THICKNESS OF SAID SHEET, (2) SAID PASSAGEWAYS EXTENDING TO AN EDGE OF SAID SHEET TO PROVIDE INGRESS AND EGRESS OPENINGS FOR A FLUID, (B) A PLURALITY OF INDIVIDUAL STRIPS OF SAID UNIT EACH INTERCONNECTING SAID MARGINAL PORTIONS, (1) SAID STRIPS EACH BEING OF A THICKNESS SUBSTANTIALLY LESS THAN THE THICKNESS OF SAID MARGINAL PORTIONS AND HAVING AN ELONGATE PORTION WHICH IS SUBSTANTIALLY RECTANGULAR IN CROSS SECTION WITH ITS MAJOR DIMENSION ALONG SUBSTANTIALLY THE FULL LENGTH THEREOF DISPOSED IN A PLANE SUBSTANTIALLY PERPENDICULAR TO THE PLANE OF SAID UNIT, SAID ELONGATED PORTION BEING INTEGRATED AT EACH END THEREOF WITH A TRANSITION BEND PORTION THROUGH WHICH SAID STRIPS ARE INTEGRATED WITH SAID MARGINAL PORTIONS OF SAID UNIT WHEREBY SAID STRIPS OVER SAID ELONGATE PORTION ARE DISPOSED IN PARALLEL SPACED APART RELATIONSHIP WITH THEIR OUTER PLANAR SURFACES IN FACE TO FACE RELATIONSHIP, THEREBY DEFINING ELONGATE APERTURES FOR THE FLOW THERETHROUGH OF AN EXTERNAL HEAT TARNSFER MEDIUM, (2) SAID STRIPS HAVING AN INTERNAL TUBULAR PASSAGEWAY DISPOSED BETWEEN SPACED APART PORTIONS OF THE THICKNESS OF SAID STRIPS, SAID LATTER PASSAGEWAYS COMMUNICATING WITH SAID PASSAGEWAYS IN SAID MARGINAL PORTIONS THEREBY PROVIDING A CONTINUOUS PATH FOR THE CIRCULATLION OF A HEAT TRANSFER MEDIUM THROUGH SAID UNIT. 